Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Accounts Receivable (Details)

v3.19.1
Summary of Significant Accounting Policies - Accounts Receivable (Details) - USD ($)
3 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Changes in the Allowance for Doubtful Accounts [Roll Forward]      
Allowance for doubtful accounts, beginning of period $ 2,765,000 $ 3,315,000 $ 3,315,000
Charges to costs and expenses 77,000 64,000  
Account write-offs and other (29,000) (86,000)  
Allowance for doubtful accounts, end of period 2,813,000 $ 3,293,000 2,765,000
Accounts receivable, amounts determined to be uncollectible $ 0   $ 0
Minimum      
Changes in the Allowance for Doubtful Accounts [Roll Forward]      
Accounts receivable retainage, percentage 5.00%    
Maximum      
Changes in the Allowance for Doubtful Accounts [Roll Forward]      
Accounts receivable retainage, percentage 10.00%